The present invention relates generally to microfluidic techniques. In particular, the invention provides a method and system for computing a cycle-threshold for pre-amplified DNA samples suspended in a volume of fluid in a chamber of a microfluidic device. More particularly, the present method and system removes baseline drift from amplification curves. Merely by way of example, the techniques for microfluidic methods and systems are applied using fluorescent, chemiluminescent, and bioluminescent readers coupled to the microfluidic device, but it would be recognized that the invention has a much broader range of applicability.
Concerted efforts to develop and manufacture microfluidic systems to perform various chemical and biochemical analyses and syntheses have occurred. Such systems have been developed for preparative and analytical applications. A goal to make such micro-sized devices arises from significant benefits achieved from miniaturization of conventional macro scale analyses and syntheses, which are often cumbersome and less efficient. A substantial reduction in time, lower costs, and more efficient space allocation are achieved as benefits using these microfluidic systems. Additional benefits may include a reduction in human operator involvement with automated systems using these microfluidic devices. Automated systems also decrease operator errors and other operator type limitations. Microfluidic devices have been proposed for use in a variety of applications, including, for instance, capillary electrophoresis, gas chromatography and cell separations.
Microfluidic devices adapted to conduct nucleic acid amplification processes are potentially useful in a wide variety of applications. For example, such devices could be used to determine the presence or absence of a particular target nucleic acid in a sample, as an analytical tool. Examples of utilizing microfluidic device as an analytical tool include:                testing for the presence of particular pathogens (e.g., viruses, bacteria or fungi);        identification processes (e.g., paternity and forensic applications);        detecting and characterizing specific nucleic acids associated with particular diseases or genetic disorders;        detecting gene expression profiles/sequences associated with particular drug behavior (e.g. for pharmacogenetics, i.e. choosing drugs which are compatible/especially efficacious for/not hazardous with specific genetic profiles); and        conducting genotyping analyses and gene expression analyses (e.g., differential gene expression studies).        
Alternatively, the devices can be used in a preparative fashion to amplify nucleic acids, producing an amplified product at sufficient levels needed for further analysis. Examples of these analysis processes include sequencing of the amplified product, cell-typing, DNA fingerprinting, and the like. Amplified products can also be used in various genetic engineering applications. These genetic engineering applications include (but are not limited to) the production of a desired protein product, accomplished by insertion of the amplified product into a vector that is then used to transform cells into the desired protein product.
Despite these potential applications, the determination of the cycle-threshold for a given nucleic acid amplification process may be characterized by errors. Therefore, there is a need in the art for improved methods and systems for computing the cycle-threshold for pre-amplified DNA samples suspended in a volume of fluid in a chamber of a microfluidic device.